Offshore Gas Platforms Research Articles

The Role of International Law Status in Recognition of Qualifications of Sailors and Workers at Offshore Oil and Gas Platforms in European Union Law

The Role of International Law Status in Recognition of Qualifications of Sailors and Workers at Offshore Oil and Gas Platforms in European Union Law

Minimizing hydrocarbon release from offshore piping by performing probabilistic fatigue life assessment

Abstract Topside piping is the major source of hydrocarbon release (HCR) on offshore oil and gas (OOG) platforms in the North Sea region. Since 21% of piping failures are caused by vibration induced fatigue (VIF), an accurate remnant fatigue life (RFL) assessment has the potential to minimize the chances of HCR from an operating piping system. BS-7910 gives two possible approaches for performing a RFL assessment: the S–N curve approach and the fracture mechanics (FM) approach. Since there are large number of uncertainties (such as uncertainty due to the crack growth model, future loading, material and geometric properties, etc.) involved in the RFL calculation process, therefore it is vital to consider the aforementioned sources of uncertainty in order to arrive at an accurate RFL estimate. Nevertheless, BS-7910 provides limited guidance on how to handle uncertainty in RFL assessment. The most common way of dealing with the aforementioned uncertainty is to evaluate RFL probabilistically. This manuscript thus explains the procedure of the probabilistic RFL assessment of offshore topside piping, with an emphasis on uncertainty quantification, propagation and management. Uncertainty quantification handles the identification and characterization of the different sources of uncertainty that may influence the future behavior of the piping component and, in turn, the RFL estimate. Thereafter, uncertainty propagation employs the formerly quantified uncertainties and utilizes the aforementioned information to estimate the RFL. Finally, uncertainty management deals with performing sensitivity analysis to find the individual contributors to uncertainty in the estimated RFL. A numerical case study illustrating the deterministic and probabilistic RFL assessment of topside piping is presented. Afterwards, probabilistically predicted RFL is used to demonstrate the calculation of an inspection interval. Finally, the implications of probabilistically estimated RFL on HCR from process piping is discussed.

Records of five bryozoan species from offshore gas platforms rare for the Dutch North Sea

This study reports on bryozoan species collected at three offshore gas platforms in the Dutch part of the North Sea. Four out of thirteen observed species are considered as rare in the Netherlands, whereas Cribrilina punctata is a new species for Dutch waters.

Explosion induced dynamic responses of blast wall on FPSO topside: Blast loading application methods

Topside areas on an offshore oil and gas platform are highly susceptible to explosion. A blast wall on these areas plays an important role in preventing explosion damage and must withstand the expected explosion loads. The uniformly distributed loading condition, predicted by Explosion Risk Analyses (ERAs), has been applied in most of the previous analysis methods. However, analysis methods related to load conditions are inaccurate because the blast overpressure around the wall tends to be of low-level in the open area and high-level in the enclosed area. The main objectives of this paper are to study the effects of applying different load applications and compare the dynamic responses of the blast wall. To do so, various kinds of blast pressures were measured by Computational Fluid Dynamics (CFD) simulations on the target area. Nonlinear finite element analyses of the blast wall under two types of identified dynamic loadings were also conducted.

Offshore oil and gas, and operational sheen occurrence: is there potential harm to marine birds?

Hydrocarbon discharges into the ocean, both regulated and accidental, occur from offshore drilling and production operations, and can result in oil sheen (≤3 μm thick) and slick (>3 μm thick) formation, potentially harming marine birds. Sheens may commonly occur around offshore oil and gas platforms in Atlantic Canada, however, there is little information on regularity of occurrence. Further, there are few direct studies on potential impacts of sheens, associated with offshore oil and gas operations, on marine birds. We reviewed potential sources and frequency of hydrocarbon accumulation on sea surfaces from offshore oil and gas operations in Atlantic Canada, and the likelihood of overlap with marine birds. We conducted a literature review on lethal and sub-lethal effects of low levels of oil contact and ingestion on marine birds, focusing on studies that describe measured dosages of oil. We extrapolated from these data on low-dose oil exposure to link possible effects to marine birds resulting from exposure to sheens. We found that sheens occur around production operations in Atlantic Canada at allowable levels of oil concentrations in produced water. Frequency and extent of occurrence cannot be estimated from current monitoring practices. While immediate lethal effects to seabirds likely are not common from external oiling of feathers from sheens, added stressors, such as cold weather, can result in external oiling from sheens having significant impact on seabird metabolic rate and can be ultimately lethal. Ingestion of small amounts of oil, doses that realistically could be expected from exposure to sheens, in some cases resulted in sub-lethal effects to adult seabirds, primarily affecting metabolic rate, sub-lethal health impacts, and reproductive output. Nestlings and eggs do not come in direct contact with sheens, yet these life stages are highly sensitive to oil, and transfer of oil from adults exposed to sheens likely is above tolerance levels at times. Negative effects to reproductive output from small doses of ingested oil could be causing undetected impacts on marine birds and marine bird populations. Lack of standardized monitoring of marine bird contact with sheens and potential harm makes assessments of magnitude and extent of impact problematic.

First evaluation of foraminiferal metabarcoding for monitoring environmental impact from an offshore oil drilling site

At present, environmental impacts from offshore oil and gas activities are partly determined by measuring changes in macrofauna diversity. Morphological identification of macrofauna is time-consuming, expensive and dependent on taxonomic expertise. In this study, we evaluated the applicability of using foraminiferal-specific metabarcoding for routine monitoring. Sediment samples were collected along distance gradients from two oil platforms off Taranaki (New Zealand) and their physico-chemical properties, foraminiferal environmental DNA/RNA, and macrofaunal composition analyzed. Macrofaunal and foraminiferal assemblages showed similar shifts along impact gradients, but responded differently to environmental perturbations. Macrofauna were affected by hypoxia, whereas sediment grain size appeared to drive shifts in foraminifera. We identified eight foraminiferal molecular operational taxonomic units that have potential to be used as bioindicator taxa. Our results show that metabarcoding represents an effective tool for assessing foraminiferal communities near offshore oil and gas platforms, and that it can be used to complement current monitoring techniques.

A dynamic model for FLNG spiral wound heat exchanger with multiple phase-change streams based on moving boundary method

For predicting the dynamic performance of spiral wound heat exchangers (SWHEs) applied in floating liquefied natural gas (FLNG) offshore platforms, a dynamic model reflecting the heat transfer among multiple phase-change streams in SWHEs is presented. In the dynamic model, a two-dimensional partitioned matrix is proposed to describe the heat transfer relations among phase-change streams in a general form; a group of generic equations based on the partitioned matrix is developed to calculate the heat capacities of phase-change streams, suitable for all types of phase zones (i.e. vapor, two-phase and liquid zones). An implicit iterative algorithm is proposed to solve the equations. The reliability and capability of the model has been partly validated by comparing the calculated steady-state performance with experimental data, and the dynamic performance under sloshing conditions are investigated, indicating that the sloshing-induced reduction of SWHE overall performance is within 5% for most cases.

Monitoring and modeling the dispersion of produced water on the Scotian Shelf

Produced water from offshore oil and gas platforms is often disposed of directly into the sea, and there has been concern that this discharge might have deleterious effects on the marine environment. To help understand the patterns of dispersion and dilution of produced water discharges, and their potential effects, a combined modeling and monitoring study was conducted. Chemical analysis of representative produced water samples recovered from the Sable Offshore Energy Project (SOEP) Venture platform showed elevated concentrations of several organic and inorganic compounds of environmental concern; however, of the 25 stations sampled within 500 m of the platform, only one station, NE50, located 50 m to the northeast, showed chemicals associated with produced water at levels significantly above background values. The Dose-related Risk and Effect Assessment Model (DREAM) was used to evaluate the fate and transport processes of produced water after discharge. The results revealed that the near background level concentrations detected at the 26 stations were due to sampling outside the narrow plume boundary. This indicated that there was no accumulation of pollutants near the platform except inside the narrow plume. The comparison of modeled and empirical data showed that the DREAM model can effectively predict plume behaviour. The results agreed well with the monitoring data and simulated the location of the plume as it changed continuously with the tidal currents. The model illustrated that elevated concentrations within the produced water plume occur only near the vicinity of the discharge.

Fire at Guneshli Oilfield in the Caspian Sea: Satellite Monitoring and Possible Causes of the Accident

In early December 2015 on the platform number 10 at Guneshli oilfield in the Caspian Sea there was a pipeline rupture and fire a number of oil and gas wells. This is the third accident in Azerbaijan’s offshore oil and gas platforms in the Caspian Sea for the last three years. For the first time in the Russian practice for monitoring the emergency platform and environmental impact all possible means of remote sensing have been used. It includes an analysis of images of three radar and nine optical satellites. There was found that on the platform oil spills occurred, it is likely due to depressurization of burning a borehole. It has been shown that at present accidents with marine oil and gas facilities can effectively monitored from space.

Meals on Wheels? A Decade of Megafaunal Visual and Acoustic Observations from Offshore Oil & Gas Rigs and Platforms in the North and Irish Seas.

A decade of visual and acoustic detections of marine megafauna around offshore Oil & Gas (O&G) installations in the North and Irish Seas are presented. Marine megafauna activity was monitored visually and acoustically by Joint Nature Conservation Committee (JNCC) qualified and experienced Marine Mammal Observers (MMO) and Passive Acoustic Monitoring (PAM) Operators respectively, with real-time towed PAM in combination with industry standard software, PAMGuard. Monitoring was performed during routine O&G industrial operations for underwater noise mitigation purposes, and to ensure adherence to regulatory guidelines. Incidental sightings by off-effort MMOs and installation crew were also reported. Visual and acoustic monitoring spanned 55 non-consecutive days between 2004 and 2014. A total of 47 marine mammal sightings were recorded by MMOs on dedicated watch, and 10 incidental sightings of marine megafauna were reported over 10 years. Species included: harbour porpoise (Phocoena phocoena), Atlantic white-sided dolphin (Lagenorhynchus acutus), white beaked dolphin (Lagenorhynchus albirostris), common dolphin (Delphinus delphis), minke whale (Balaenoptera acutorostrata), common seal (Phoca vitulina), grey seal (Halichoerus grypus) and, basking shark (Cetorhinus maximus). Passive Acoustic Monitoring was conducted on two occasions in 2014; 160 PAM hours over 12 days recorded a total of 308 individual clicks identified as harbour porpoises. These appear to be the first such acoustic detections obtained from a North Sea drilling rig whilst using a typically configured hydrophone array designed for towing in combination with real-time PAMGuard software. This study provides evidence that marine megafauna are present around mobile and stationary offshore O&G installations during routine operational activities. On this basis, Environmental Impact Assessments (EIAs) for decommissioning O&G platforms should be carried-out on a case-by-case basis, and must include provisions for hitherto overlooked marine megafauna.

Energy efficiency measures for offshore oil and gas platforms

Oil and gas platforms are energy-intensive systems – each facility uses from a few to several hundreds MW of energy, depending on the petroleum properties, export specifications and field lifetime. Several technologies for increasing the energy efficiency of these plants are investigated in this work. They include: (i) the installation of multiple pressure levels in production manifolds, (ii) the implementation of multiphase expanders, (iii) the promotion of energy and process integration, (iv) the limitation of gas recirculation around the compressors, (v) the exploitation of low-temperature heat from the gas cooling steps, (vi) the downsizing or replacement of the existing gas turbines, and (vii) the use of the waste heat from the power plant. The present study builds on four actual cases located in the North and Norwegian Seas, which differ by the type of oil processed, operating conditions and strategies. The benefits and practical limitations of each measure are discussed based on thermodynamic, economic and environmental factors. Significant energy savings and reductions in CO2-emissions are depicted, reaching up to 15–20%. However, they strongly differ from one facility to another, which suggests that generic improvements can hardly be proposed, and that thorough techno-economic analyses should be conducted for each plant.

The Effects of Anthropogenic Structures on Habitat Connectivity and the Potential Spread of Non-Native Invertebrate Species in the Offshore Environment.

Offshore structures provide habitat that could facilitate species range expansions and the introduction of non-native species into new geographic areas. Surveys of assemblages of seven offshore oil and gas platforms in the Santa Barbara Channel revealed a change in distribution of the non-native sessile invertebrate Watersipora subtorquata, a bryozoan with a planktonic larval duration (PLD) of 24 hours or less, from one platform in 2001 to four platforms in 2013. We use a three-dimensional biophysical model to assess whether larval dispersal via currents from harbors to platforms and among platforms is a plausible mechanism to explain the change in distribution of Watersipora and to predict potential spread to other platforms in the future. Hull fouling is another possible mechanism to explain the change in distribution of Watersipora. We find that larval dispersal via currents could account for the increase in distribution of Watersipora from one to four platforms and that Watersipora is unlikely to spread from these four platforms to additional platforms through larval dispersal. Our results also suggest that larvae with PLDs of 24 hours or less released from offshore platforms can attain much greater dispersal distances than larvae with PLDs of 24 hours or less released from nearshore habitat. We hypothesize that the enhanced dispersal distance of larvae released from offshore platforms is driven by a combination of the offshore hydrodynamic environment, larval behavior, and larval release above the seafloor.

Safety climate and increased risk: The role of deadlines in design work

Although much research indicates positive safety climate is associated with reduced safety risk, we argue this association is not universal and may even be reversed in some contexts. Specifically, we argue that positive safety climate can be associated with increased safety risk when there is pressure to prioritize production over safety and where workers have some detachment from the consequences of their actions, such as found in engineering design work. We used two indicators of safety risk: use of heuristics at the individual level and design complexity at the design team level. Using experience sampling data ( N = 165, 42 design teams, k = 5752 observations), we found design engineers’ perceptions of team positive safety climate were associated with less use of heuristics when engineers were not working to deadlines, but more use of heuristics when engineers were working to deadlines. Independent ratings were obtained of 31 teams’ designs of offshore oil and gas platforms ( N = 121). For teams that worked infrequently to deadlines, positive team safety climate was associated with less design complexity. For teams that worked frequently to deadlines, positive team safety climate was associated with more design complexity.

Enhancing offshore process safety by selecting fatigue critical piping locations for inspection using Fuzzy-AHP based approach

Topside piping is the single largest source of the hydrocarbon releases (HCRs) on the offshore oil and gas (OOG) platforms in the North Sea region. Consequently, if the leaked hydrocarbons from the process pipework are ignited, it may lead to a catastrophic event, thereby causing significant economic losses, environmental damage, and posing serious threat to the safety of the onboard personnel. In order to avert such a fateful event and to enhance process safety, it is vital to maintain the technical integrity of the topside piping. In regard to this, risk based inspection (RBI) plays a vital role, as the inspection locations and frequency are decided based on the risk of potential failure. However, international standards such as API 570, API 581 and DNV RP-G101 provide limited guidance in regard to inspection of the fatigue degradation of the offshore topside piping. Due to the aforementioned, selection of the fatigue critical piping locations for inspection, is currently done either on the ad-hoc basis or using the three staged Risk Assessment Process (RAP) mentioned in the Energy Institute (EI) guidelines. Nevertheless, it has been revealed that the methodology for stage 1 of the RAP is laborious and time consuming. Thus, to reduce the toil of the practicing inspection engineer and with the aim of mitigating the dearth of RBI methodologies for topside piping fatigue, this manuscript proposes a Fuzzy-Analytical Hierarchy Process (FAHP) centered approach for selecting the fatigue critical piping locations for inspection and repair. The usability of the proposed approach is demonstrated by an illustrative case study.

Model Predictive Control of Offshore Power Stations With Waste Heat Recovery

The implementation of waste heat recovery units on oil and gas offshore platforms demands advances in both design methods and control systems. Model-based control algorithms can play an important role in the operation of offshore power stations. A novel regulator based on a linear model predictive control (MPC) coupled with a steady-state performance optimizer has been developed in the simulink language and is documented in the paper. The test case is the regulation of a power system serving an oil and gas platform in the Norwegian Sea. One of the three gas turbines is combined with an organic Rankine cycle (ORC) turbogenerator to increase the energy conversion efficiency. Results show a potential reduction of frequency drop up to 40% for a step in the load set-point of 4 MW, compared to proportional–integral control systems. Fuel savings in the range of 2–3% are also expected by optimizing on-the-fly the thermal efficiency of the plant.

Impact of offshore gas platforms on the structural and functional biodiversity of nematodes

The Mediterranean Sea hosts hundreds of offshore gas platforms, whose activity represents a potential threat to marine ecosystems. Evidence from several studies indicates that nematodes can be highly sensitive to changes in the environmental quality. Here, we investigated the response of nematode assemblages to the presence of offshore gas platforms (located in the central Mediterranean Sea) in terms of spatial heterogeneity, structural and functional diversity. Since the effect of the investigated offshore platforms on macrofaunal assemblages were previously assessed by Terlizzi et al. (2008), the study provided also the opportunity to compare the response of different benthic compartments to the same impact related to fossil fuel extraction on marine environments. The platforms had a significant impact on nematode assemblages up to 1000 m distance from the structure. The effects were evident in term of: a) more homogeneous spatial distribution of nematode assemblages, b) increased trophic diversity of deposit feeders and c) changes in life strategies with an increase of opportunistic species in sediments closer to the platforms. Such effects seemed to be related to the dimension of the platform structures, rather than to chemical pollution or changes in food availability. These findings suggest that the platforms exert a physical alteration of the surrounding environment that is reflected by altered structural and functional traits of nematode biodiversity. The use of nematodes for monitoring the effects of the platforms only partially matched with the results obtained using macrofauna, providing further insights on potential outcomes on the functional response of marine assemblages to fossil fuel extraction.

Potential influence of offshore oil and gas platforms on the feeding ecology of fish assemblages in the North Sea

This article presents results from the first detailed study on the feeding habits of fish assemblages associated with offshore oil and gas platforms in the North Sea. Multi-seasonal sam- pling was conducted at one of the oil platforms located in the central North Sea between Septem- ber 2010 and January 2014 to characterise temporal variation in the stomach contents of different fish species. A total of 6 fish species were recorded, including commercially important gadoids such as saithe Pollachius virens, haddock Melanogrammus aeglefinus and cod Gadus morhua. Saithe fed predominantly on euphausiids and haddock consumed a large proportion of ophi- uroids, whereas cod were mainly piscivorous. The prey compositions were significantly different between species, indicating the presence of interspecific prey resource partitioning among those species. To further investigate possible links between the feeding habits of the most dominant fish species, saithe, and the physical presence of offshore platforms across the North Sea, a separate set of stomach data was collected during the 2012 Quarter 3 International Bottom Trawl Survey aboard the FRV 'Scotia'. The multivariate analysis of both data sets showed that the observed spatio-temporal variability in the saithe diet was significantly explained by proximity to the near- est offshore platforms and changes in water temperatures, which appear to reflect patterns of euphausiid availability over space and time. The physical presence of the offshore structures may potentially affect the distribution/availability of zooplankton (i.e. euphausiids) and thereby influ- ence the feeding behaviour of saithe and any other marine populations that are interconnected to the dynamics of such trophic interactions.

Marine Fouling Assemblages on Offshore Gas Platforms in the Southern North Sea: Effects of Depth and Distance from Shore on Biodiversity.

Offshore platforms are known to act as artificial reefs, though there is on-going debate on whether this effect is beneficial or harmful for the life in the surrounding marine environment. Knowing what species exist on and around the offshore platforms and what environmental variables influence this species assemblage is crucial for a better understanding of the impact of offshore platforms on marine life. Information on this is limited for offshore platforms in the southern North Sea. This study aims to fill this gap in our knowledge and to determine how the composition and the abundance of species assemblages changes with depth and along a distance-from-shore gradient. The species assemblages on five offshore gas platforms in the southern North Sea have been inventoried using Remotely Operated Vehicles inspection footage. A total of 30 taxa were identified. A Generalised Additive Model of the species richness showed a significant non-linear relation with water depth (p = 0.001): from a low richness in shallow waters it increases with depth until 15–20 m, after which richness decreases again. Using PERMANOVA, water depth (p≤0.001), community age (p≤0.001) and the interaction between distance from shore and community age (p≤0.001) showed a significant effect on the species assemblages. Future research should focus on the effect additional environmental variables have on the species assemblages.

Automatic extraction of offshore platforms using time-series Landsat-8 Operational Land Imager data

Offshore oil and gas platforms are rapidly expanding worldwide to meet the growing demand for energy, and up-to-date knowledge of their number and spatial distribution is essential for management and safety maintenance of the marine environment. However, information on the distribution of these platforms over vast areas of the sea is extremely poor — partly because of business secrecy, national interests including security, and partly from bureaucratic inertia. Until recently, the automatic and accurate identification of platforms using optical imagery was challenging due to their subtle characteristics (i.e., low contrast and small size) and prevalent cloud cover. The Landsat-8 satellite, with its increasing Operational Land Imager (OLI) dataset with uniform quality and global coverage, may assist researchers in assessing the worldwide distribution of offshore platforms. Here we describe an automated method, based on time-series of OLI imagery, for extracting offshore platforms (AMEOP) which addresses the aforementioned problems. Specifically, two strategies (time-series and multi-refinement) were designed to address the challenges presented by heavy cloud cover over the sea. Three features documented in the OLI imagery time-series (contextual feature, and position- and size-invariance) were used to accurately discriminate offshore platforms from false positives. The AMEOP was applied to the Gulf of Thailand and 370 offshore platforms were automatically identified using 198 OLI images. Validation using Synthetic Aperture Radar (SAR) images and Chinese high-resolution satellite imagery demonstrated an omission error of 3.8% and a commission error below 1.0%. The AMEOP was also successfully extended to the Persian Gulf and northern Gulf of Mexico, 2346 and 2411 offshore platforms were respectively identified. We believe that the methodology presented herein provides a robust and cost-effective technique for improving the identification of offshore platforms over large areas of the sea; and that the accumulation of OLI data, together with the SAR images, has great potential for mapping and tracking of offshore platforms on a global scale, as well as for providing an early warning of oil spills around platforms and the improved estimation of their greenhouse gas emissions.

Distribution of the invasive Caprella mutica Schurin, 1935 and native Caprella linearis (Linnaeus, 1767) on artificial hard substrates in the North Sea: separation by habitat

Studying offshore natural and artificial hard substrates in the southern North Sea (51oN–57oN/1oW–9oE), the invasive introduced Japanese skeleton shrimp Caprella mutica Schurin, 1935 was found to co-exist with the native Caprella linearis (Linnaeus, 1767) only on near-shore locations that had an intertidal zone (e.g., wind farm foundations). In contrast, on far offshore and strictly subtidal locations, such as shipwrecks and rocky reefs, only C. linearis was found. Based on these exploratory observations, we hypothesised that artificial structures that are only subtidal are inhabited exclusively by C. linearis, and never by C. mutica. To test this hypothesis and understand factors driving each species’ habitat preferences, habitat suitability models were constructed using generalised additive models, based on samples collected in 2013–2015 from offshore gas platforms, buoys, shipwrecks, and rocky reefs and combined with data from other published and unpublished surveys (2001–2014). The models showed that the presence of C. mutica is explained by the availability of intertidal and floating hard substrates, suspended particulate matter density (SPM), mean annual sea surface temperature, salinity, and current velocity. The C. linearis model included subtidal hard substrates, SPM, salinity, temperature, and current velocity. The modelled distributions showed a significant difference, demonstrating that C. linearis’ habitat preference does not fully overlap with that of C. mutica. Thus, the native and alien Caprella species are likely to be able to co-exist in the North Sea.